JPH11328297A - Optical reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately select light of plural wavelengths and to use it even if a light source is one. SOLUTION: This optical reader 10 irradiates a medium 4 that is an object with light from a light source 18 so as to gather rays of reflected light from the medium 4 on a CCD 22 that is a photodetector through a lens 21. The reader 10 is provided with plural filters 32 and 33 having different characteristics in front of the lens 21 in a light path of the reflected light in an insertable and detachable way and can limit and also switch a use frequency among emission wavelengths of the source 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical reader. More specifically, the present invention relates to an optical reader that uses light having a wavelength corresponding to a subject or the like.

[0002]

2. Description of the Related Art In an optical reading apparatus for reading bar codes, characters, and the like, it is common to use infrared light as a light source to separate dirt and read characters from the background. On the other hand, the use of light other than infrared light may be suitable depending on the use conditions such as the type of ink for the read character, the color of the ink used for the background of the read character, and the use of the optical reader. Alternatively, red light, yellow light (LED), white light (fluorescent tube), or the like may be used as a light source. That is, in the conventional optical reading apparatus, one type of light source suitable for the use is previously selected and provided.

[0003]

However, since the above-mentioned optical reader has only one kind of light source, a plurality of wavelengths cannot be appropriately switched and used. In this case, by providing a plurality of light sources of different types, it becomes possible to select and use light of different wavelengths by switching the light sources, but this leads to an increase in the size of the device and a significant increase in cost. It is not practical.

[0004] It is an object of the present invention to provide an optical reader capable of appropriately selecting and using light of a plurality of wavelengths even with one light source.

[0005]

In order to achieve the above object, the invention according to claim 1 irradiates light from a light source to a subject, and condenses reflected light from the subject on a light receiving element via a lens. In the optical reading device, a plurality of filters having different characteristics are provided in front of the lens so that they can be inserted into and removed from the optical path of the reflected light, so that the used wavelength among the emission wavelengths of the light source can be limited and switched. is there.

Therefore, the reflected light from the subject passes through the filter and reaches the light receiving element. The light passing through the filter is limited to the wavelength of the specific frequency band according to the characteristics of the filter, so the wavelength of the light condensed on the light receiving element can be changed by switching multiple filters with different characteristics. it can. That is, even when the light of the same light source is used, the used wavelength can be switched according to the subject or the like.

Further, the optical reader according to the second aspect is
The thicknesses of the plurality of filters are different so as to make the optical path length uniform. If the wavelength of the light restricted by the filter, that is, the light passing through the filter differs, the optical path length also changes. However, since the optical path length is made uniform by changing the thickness of each filter, a clear image can be obtained over a wide range of the subject even when a light receiving element with a small depth of field is used for light from the same light source. Can be.

The optical reader according to claim 3 is
The filter is formed by applying a coating film that cuts light in a predetermined band on the surface of the optically transparent substrate, and the optical path length is made uniform by changing the thickness of the optically transparent substrate. . Therefore, when the thickness of the optically transparent substrate is changed, the thickness of the entire filter changes, and the optical path length also changes.

Further, the optical reading device according to the fourth aspect of the present invention,
The light source has an emission band in which the wavelength used can be switched by a plurality of filters. Light emitted from the light source includes light of various wavelengths. However, the light passing through the filter is limited to a specific wavelength, and then focused on a light receiving element.

Further, in the optical reader according to the fifth aspect, the plurality of filters are mounted on a filter mounting member, and a drive mechanism for switching the position of the filter mounting member is connected to the filter mounting member. . Therefore, when the drive mechanism switches the position of the filter mounting member, the position of each filter changes and the filters that allow light to pass through are switched.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on the best mode shown in the drawings.

FIGS. 1 and 2 show an example of an embodiment of an optical reader to which the present invention is applied. Optical reader 10
Is a light source 18 fixed to the holder 17, a glass plate 19 for irradiating the medium 4 such as a check or a passbook with irradiation light from the light source 18, and a reflection for changing the direction of reflected light reflected on the upper surface 4a of the medium 4. The apparatus includes a mirror 20, a lens 21 for condensing light reflected by the reflecting mirror 20, and a CCD 22, which is a light receiving element for converting a light beam from the lens 21 into an electric signal. A plurality of filters having different characteristics are provided between the reflecting mirror 20 and the lens 21. In the present embodiment, two filters 32 and 33 are provided in front of the lens 21.

The holder 17 is fixed in the case 10a of the optical reader 10 with screws 23. The light source 18
When the medium 4 is conveyed below the optical reading device 10, light is emitted, and the light is radiated through the condenser lens 31. The light source 18 has a light emission band in which the use wavelength can be switched by the filters 32 and 33. That is, for example, a fluorescent lamp, a tungsten lamp, a xenon lamp, a white lamp, or the like, which emits light over a wide wavelength, is used as the light source 18. The light emitted from the light source 18 includes light of various wavelengths, and this light is
When the light passes through one of the filters 2 and 33, the light is limited to a wavelength in a specific band corresponding to the characteristics of the filter 32 or 33 and is condensed on the CCD 22.

The reflecting mirror 20 is attached to an upper portion 25a of a bracket 25 fixed to the case 10a with screws 24. The upper portion 25a is bent toward the lens 21 so as to direct the reflected light from the medium upper surface 4a to the lens 21.

The glass plate 19 is fixed to a medium guide portion 10b of a case 10a protruding toward the medium passage so as to be located between the light source 18 and the medium 4.

Further, the optical system of the optical reading apparatus 10 is designed to reduce the loss of light amount to the lens 21 and to improve the reading angle of a bar code or the like printed on the medium 4 so that the irradiation light is irradiated on the upper surface of the medium. The direction of the reflected light at the lens coincides with the optical axis of the lens 21, that is, the optical axis of the condenser lens 31 and the lens
The optical axes are provided so as to coincide with one optical axis.

Two filters 32, 33 having different characteristics
Is mounted on the filter mounting member 34. A drive mechanism 35 for switching the position of the filter mounting member 34 is connected to the filter mounting member 34. Therefore, when the drive mechanism 35 switches the position of the filter mounting member 34, the position of each filter 32, 33 changes, and the filters 32, 33 that allow light to pass through are switched. That is, a plurality of filters 32 and 33 having different characteristics are provided in the optical path of the reflected light so as to be able to be inserted and removed, and it is possible to limit and switch the wavelength used among the emission wavelengths of the light source 18.

The drive mechanism 35 is, for example, a solenoid as shown in FIG. The tip of the solenoid 35 is connected to the filter mounting member 34. Therefore, the filter mounting member 34 is driven by the solenoid 35, and switches the filters 32 and 33 through which the reflected light passes. A hole 34a is formed in a portion of the filter mounting member 34 through which the reflected light passes, as shown in FIG. 4, so that the light is not blocked.

The thicknesses of the filters 32 and 33 are different so that the optical path length is uniform. Specifically,
As shown in FIG. 4, for example, each of the filters 32 and 33 is formed by applying a coating film 37 for cutting light in a predetermined band on the surface of an optical transparent substrate 36. By changing the thickness, the entire thickness of the filters 32 and 33 changes, and the optical path length can also change.
When the wavelength of the reflected light is changed by driving the solenoid 35 to switch the filters 32 and 33, the optical path length also changes. However, by changing the thickness of each filter 32 and 33, the wavelength of the reflected light can be changed. Can change the difference in optical path length (chromatic aberration) due to the difference in wavelength,
Even if a light receiving element having a shallow depth of field is used, a clear image can be obtained over a wide range for a subject.

In this embodiment, the first filter 32 has eight filters.
The second filter 33 is a visible light cut filter that cuts less than 800 nm. The optically transparent substrate 36 is, for example, a glass plate or the like. Note that, as in the optical reading device 10 of the present embodiment, the subject is the medium 4 traveling in the medium passage, and when the feature formed on the surface of the medium 4 is read as an image signal, the feature is used. Is a barcode written with ink such as carbon, the second filter 33 is used. Otherwise, the first filter 33 is used.
Is set to use the filter 32 of FIG.

The control device of the optical reader 10 is C
FIG. 5 is for controlling the image signal from the CD 22.
As shown in FIG.
/ D) Based on the white reference level in the white reference memory 30, the image signals from the converter 27 and the A / D converter 27 are subjected to shading correction by setting a portion having a higher reflectance than white exceeding the white reference level as white. To perform shading processing circuit 28,
A halftone processing circuit 29 for removing pseudo halftone processing (binarization processing) and moiré, and a white reference memory 30 storing a white reference level corresponding to shading by the light source 18 are stored. In this embodiment, a line CCD is used as the CCD 22.

The operation of the embodiment configured as described above will be described. Media 4 is transported through the media path and media 4
Is transported below the optical reader 10, the medium 4 is detected by a sensor (not shown), and the light source 18 emits light.

The irradiation light from the light source 18 is
Passes through the glass plate 19 and is reflected by the medium upper surface 4a. The reflected light is refracted by the reflecting mirror 20, passes through the filter 32 or 33, enters the CCD 22 along the optical axis of the lens 21, is converted into an electric signal, and is converted into an ink character or bar formed on the medium upper surface 4a. Features such as codes are read optically.

That is, the image signal converted by the CCD 22 is amplified by an amplifier 26, A / D converted by an A / D converter 27, and subjected to shading correction in a shading processing circuit 28. The image signal from the shading processing circuit 28 is subjected to pseudo halftone processing (binarization processing) and moire removal by the halftone processing circuit 29, and the features formed on the upper surface 4a of the medium are read.

In order to read the above-mentioned characteristics formed on the upper surface 4a of the medium, the filters 32 and 33 are selected to select the upper surface 4a of the medium.
Since light in the wavelength band determined in consideration of the color of a, the type of ink, and the like is used, good reading can be performed.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above description, the case where the optical reading device 10 is used for reading the characteristics of the medium upper surface 4a has been described. However, the present invention is not limited to this. In this case, the filters 32 and 33 are switched according to the subject. For example, when scanning characters, barcodes, and the like written with ink such as carbon, the second filter 33 is used. In this case, the reading wavelength is infrared light. On the other hand, the first filter 32 is selected when the ink ribbon is other than infrared light (or cannot be understood), or when ordinary so-called Laplace scanning is performed.
In these cases, the reading wavelength is visible light. Further, for example, when scanning a character in which the background design is written in red and the ink is written in black or the like, an application such as erasing the background design using a red filter may be considered. Further, for example, an application of reading an embossed character or the like formed on the medium 4 can be considered. Switching between the filters 32 and 33 can be easily performed by the drive mechanism 35.

In the above description, two filters 3
Although the configuration is such that the number of filters is switched between 2 and 33, the number of filters to be switched is not limited to two, and three or more filters may be switched.

Further, the case where a solenoid is used as the drive mechanism 35 has been described, but an actuator such as a motor may be used.

[0029]

As described above, in the optical reading device according to the first aspect, a plurality of filters having different characteristics are provided in front of the lens so as to be inserted into and removed from the optical path of the reflected light. Since the wavelength used can be limited and switched, the wavelength of the light focused on the light receiving element changes by switching the filter. That is, even if the same light source is used, the reading wavelength can be changed, and it is not necessary to prepare a plurality of light sources, so that the apparatus has a simple structure, so that the apparatus can be miniaturized and increase in production cost can be suppressed. .

In this case, it is preferable that the thicknesses of the plurality of filters are made different so that the optical path lengths are made uniform, as in the optical reader according to the second aspect. By doing so, even when the frequency of the light passing therethrough is changed by switching the filter, the difference in the optical path length can be absorbed,
The imaging performance can be improved, and a clear image can be obtained over a wide range of the subject even when a light receiving element having a small depth of field is used.

Further, as in the optical reader according to the third aspect, the filter is formed by applying a coating film for cutting light in a predetermined band on the surface of the optically transparent substrate. It is preferable to make the optical path length uniform by changing the thickness. By doing so, the optical path length difference can be easily absorbed.

In the optical reader according to the fourth aspect, since the light source has a light emission band in which the wavelength used can be switched by a plurality of filters, the light emitted from the light source includes light of various wavelengths. By switching the filters through which this light passes, various operating wavelengths can be obtained using one light source.

Further, in the optical reader according to the fifth aspect, a plurality of filters are mounted on the filter mounting member, and the drive mechanism for switching the position of the filter mounting member is connected to the filter mounting member. Can be switched.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of an optical reader according to the present invention.

FIG. 2 is an enlarged cross-sectional view illustrating a periphery of a light source of the optical reading apparatus of FIG.

FIG. 3 is a schematic configuration diagram showing a filter mounting member and a driving mechanism of the optical reader of FIG. 1;

FIG. 4 is a sectional view of a filter of the optical reader of FIG. 1;

FIG. 5 is a block diagram illustrating a configuration of a control device.

[Explanation of symbols]

 Reference Signs List 3 medium passage 4 medium (subject) 10 optical reader 18 light source 21 lens 22 CCD (light receiving element) 32, 33 filter 34 filter mounting member 35 solenoid (drive mechanism) 36 optical transparent substrate 37 coating film

Claims (5)

[Claims] 1. An optical reading apparatus which irradiates light from a light source to a subject and condenses reflected light from the subject to a light receiving element via a lens. An optical reading device characterized in that the filter described in (1) is provided in the optical path of the reflected light so as to be able to be inserted into and removed from the optical path of the reflected light so as to limit and switch the wavelength used among the emission wavelengths of the light source. 2. The filter according to claim 1, wherein the thicknesses of the plurality of filters are different so as to make the optical path length uniform.
An optical reader according to claim 1. 3. The filter is formed by applying a coating film for cutting light in a predetermined band on the surface of an optically transparent substrate, and the optical path length is made uniform by changing the thickness of the optically transparent substrate. 3. The optical reader according to claim 2, wherein the reading is performed. 4. The optical reader according to claim 1, wherein the light source has a light emission band in which a use wavelength can be switched by the plurality of filters. 5. The filter according to claim 1, wherein the plurality of filters are mounted on a filter mounting member, and a drive mechanism for switching a position of the filter mounting member is connected to the filter mounting member. An optical reader according to any of the preceding claims.